Method and apparatus for finishing the tooth surfaces of hypoid gears

ABSTRACT

A hypoid gear finishing method and apparatus wherein either two hypoid pinion gears or a hypoid ring gear are formed as the tool in a specified shape, the other being rough-cut as the workpiece, the two hypoid pinion gears being opposied to each other and meshed with the hypoid ring gear, and torques in opposite directions are given to the two hypoid pinion gears to rotate these hypoid pinion gears, thereby burnishing the tooth surface of the workpiece gear.

United States Patent 1191 Takahashi et a1.

[ METHOD AND APPARATUS FOR FINISHING THE TOOTH SURFACES OF HYPOID GEARS [75] Inventors: Akira Takahashi, Okazaki;

Masahiro Kuwabara, Toyota, both of Japan [73} Assignee: Toyota Jidosha Kogyo Kabushiki Kaisha, Toyota, Aichi-prefecture, Japan [22] Filed: Apr. 6, 1972 [21] Appl. No.: 241,606

[30] Foreign Application Priority Data Apr. 6, 1971 Japan 46-.21231 Apr. 23, 1971 Japan 46-26541 [52] US. Cl 51/89, 51/26, 51/89, 51/105 R, 51/287, 29/90 B [51] Int. Cl B241) 39/00 [58] Field of Search 51/287, 88, 89, 26, 105 R; 29/90 R, 90 B [56] References Cited UNITED STATES PATENTS v 1.878.603 9/1932 Robinson 51/26 1111 39,813,821 [451 June 4,1974

1,879,089 9/1932 Christman ..51/287 533,863 2/1895 Brandes "51/26 1,858,568 5/1932 Wildhaber 51/287 1,676,371 7/1928 Wildhaber 51/287 X 2,711,673 6/1955 Miller .Q 51/287 X 3,099,901 8/1963 Hunkelermn' i 51/287 X 3,403,569 10/1968 Lautenschlager.... 51/287 X 1,796,484 5/1931 Slade i 29/90 B 1,821.188 9/1931 McMullen.... 29/90 B 1.858.044 5/1932 Head i i 29/90 B 2,112,996 4/1938 Perkins 29/90 B Primary ExaminerDonald G. Kelly Attorney, Agent, or FirmRichard K, Stevens et a1.

[ 57 ABSTRACT A hypoid gear finishing method and apparatus wherein either two hypoid pinion gears or a hypoid ring gear are formed as the tool in a specified shape, the other being rough-cut as the workpiece, the two hypoid pinion gears being opposied to each other and meshed with the hypoid ring gear, and torques in 0pposite directions aregiven to the two hypoid pinion gears to rotate these hypoid pinion gears, thereby burnishing the tooth surface of the workpiece gear.

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PATENTEDJun 4 m4 SHEU 050$ 11 PATENTEB- 4 B sum osor11 PATENTEDJ 4 7 sum 0anF11 PATENTEUJUH 4 m4 saw our 11 N v GMT A U; W V N NS J m N m! N w n METHOD AND APPARATUS FOR FINISHING THE TOOTH SURFACES OF I-IYPOID GEARS BACKGROUND OF THE INVENTION Smooth rotation and low noise are the requirements of hypoid gears which are commonly subjected to highspeed rotation in vehicles.

To meet this requirement the finishing of hypoid gears includes rough-cutting followed by finish-cutting on a lathe or the like and then lapping to smoothen the tooth surface and thereby improve the tooth contact. The work efficiency after rough-cutting is so poor and the work expense is so high that there is a need for reducing the number of work steps.

SUMMARY OF THE INVENTION The primary object of the present invention is to provide a method for burnishing the tooth surface of a rough-cut hypoid gear, to render the tooth surface of the gear to a desired dimensional precision and assure the best tooth contact, thereby substantially increasing work efficiency and saving work expense when compared with the conventional cutting and finishing method.

Another object of the present invention is to substantially prolong the service life of the burnishing tools, thereby facilitating the maintenance of good tooth contact.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view showing the arrangement of workpiece and tool.

FIG. 2 is a schematic diagram illustrating one embodiment of the inventive method.

FIG. 3 is an oblique view of the arrangement in FIG. 1.

FIGS. 4 and 5 are sectional views along line IXIX of the arrangement in FIG. 1, illustrating the contact condition between tooth surfaces of the tool and the workpiece being machined.

FIGS. 6 and 7 are also sectional views along line XX of the arrangement in FIG. 1 illustrating the contact condition between tooth surfaces of the tool and the workpiece.

FIG. 8 is a schematic diagram of another embodiment of the present invention.

FIG. 9 is a sectional view along line IXIX of the arrangement in FIG. 1.

FIG. 10 is a sectional view along line XX of the arrangement in FIG. I.

FIG. 11 is a diagram showing the contact line of a driving tooth-surface of the workpiece gear and the shifting direction of said contact line.

FIG. 12 is a diagram showing the contact line of the coasting tooth surface of the workpiece gear and the shifting direction of said contact line.

FIG. 13 is a vertical cross-sectional view of the tooth trace of the workpiece gear.

FIG. 14 is a schematic diagram of still another-embodiment of the inventive method.

FIG. 15 is a plan view of apparatus embodying the invention as schematically illustrated in FIG. 2.

FIG. 16 is a side view of the apparatus illustrated in FIG. 15.

FIG. 17 is a cross-sectional view of the apparatus of 'FIG. 15 taken along line AA.

FIG. 18 is a cross-sectional view of the apparatus of FIG. I5 taken along line BB.

FIG. 19 is a cross-sectional view of the apparatus of FIG. 15 taken along line CC.

FIG. 20 is a cross-sectional view of the apparatus of FIG. 15 taken along line DD.

FIG. 21 is a partially schematic view illustrating the brake drum and lever shown in FIG. 20.

FIG. 22 is a cross-sectional view of the apparatus illustrated in FIG. 16 taken along line E-E.

, FIG. 23 is a cross-sectional view of an apparatus embodying the invention as schematically illustrated in FIG. 8, taken along a line corresponding to line AA in FIG. 15.

FIG. 24 is a partial cross-sectional view of an apparatus embodying the invention as schematically illustrated in FIG. 8 taken along a line corresponding to line E-E in FIG. 16.

FIG. 25 is a cross-sectional view of an apparatus embodying the invention as schematically illustrated in FIG. 14 taken along the axes of shafts 104 and 105.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 to 7, a description is made of the first embodiment of the present invention, in which a special .hypoid ring gear, which meshes with the whole tooth surface of a hypoid pinion gear finished to specified dimensions, is used as a tool and a rough-cut hypoid pinion gear is used as a workpiece.

In these figures, l and 2 are hypoid pinion gears (hereafter to be simply referred to as the workpiece), and a hypoid ring gear 3 (hereafter to be simply referred to as the tool) is made to mesh therewith. The workpieces l and 2, which are to be finished to a shape of specified dimensions, must be arranged in an adequate position. Now the arrangement of the workpieces l and 2 in relation to the tool 3 is described referring to the power transmission system shown in FIG. 2.

Using a tooth-positioning device, hypoid pinion gears (hereafter to be called master gears), finished to normal size and normal tooth contact by the conventional method, are fitted to the internal ends of shafts 4 and 5. The tool 3 is fitted to the tip of a shaft 6 in a position matching the master gears by means of the toothpositioning device. Thereupon, a hydraulic cylinder 7 linked to the shaft 6 is operated to move the tool 3 forward to engage the master gears. Thereby, through adjustment of positioning members 8 and 9 of the shaft 6 an appropriate circumferential gap is created between the teeth of the tool 3 and the master gears. The tooth surfaces of the tool 3 are then coated with red lead.

Then motor 10 is operated, and while braking shaft .6 which has a brake drum l2 thereon operated through brake lever 11, the tooth contact between the tool 3 and the master gears is checked, and the shafts 4 and 5 to which the master gears are fitted, are adjusted in their longitudinal directions, and both of these shafts 4 and 5, and the shaft 6 are adjusted in directions normal to the shaft of the workpiece in such a manner that adequate tooth contact may be assured on the tooth surface of the tool.

Thus with the relative positions of the master gears to the tool 3 perfectly adjusted, the workpieces 1 and 2 are finished in the following manner.

The master gears are taken away from the shafts 4 and 5. The workpieces l and 2 are fitted to the shafts 4 and 5. Then hydraulic cylinder '7 is operated to move the tool 3 forward to engage the workpieces 1 and 2. Next the motor is driven in such a manner that the workpieces 1 and 2 and the tool 3 run in the directions indicated by the arrows in FIG. 1, whereupon the rotation of the motor 10 will be diverted by bevel gears 14 and 14 via a bevel gear 13 into opposite directions.

The rotation of the motor 10, which has been diverted by the bevel gear 13 to the right direction, i.e., transmitted to the bevel gear 14, changes its direction again by the bevel gears and 16, and after being reduced in speed by the planetary reducing system composed of an internal gear 17, a sun gear 18 and planet gears 19, is transmitted to a bevel gear 20, and then to a bevel gear 21 which meshes with the bevel gear 20, thereby turning the workpiece 1 through a bevel gear 22 which rotates together with the bevel gear 21 and through a bevel gear 23 fixed to the shaft 4.

Similarly, the rotation of the motor 10 diverted in the left direction by a bevel gear 14' changes its direction by bevel gears 15' and 16, and, after being reduced in speed by the planetary reducing system composed of an internal gear 17' a sun gear 18' and a planet gear 19, is transmitted to bevel gears 20 and 21'. Further, through a bevel gear 22 which runs together with the bevel gear 21 and through a bevel gear 23' fixed to the shaft 5, the workpiece 2 is turned. Thus, the workpieces 1 and 2 making the same amount of rotation in mutually opposite directions cause the tool .3 to turn. A hydraulic cylinder with a rack 24 which meshes with internal gear 17 is also thereby operated, and rack 24 is moved in the direction in which workpiece l, for example, is accelerated, and the internal gear is turned. As the rotation of internal gear 17 is transmitted throughout the power transmission system, the workpieces 1 and 2 are twistingly turned through the tool 3.

The contact state between tooth surfaces of the tool 3 and the workpieces 1 and 2 in the above condition is illustrated in FIG. 3; namely, the tooth surface (a) of the workpiece 1 is in contact with only the driving side (b) of the tool 3 (see FIG. 4), while the tooth surface (0) of the workpiece 2 is in contact with only the coasting side of the tool 3 (see FIG. 6). Therefore, when the rack 24 is axially shifted by the action of the hydraulic cylinder 25 and moved in one direction a distance set by a positioning member 27, the tooth surface (a) of the workpiece 1 and the tooth surface (c) of the workpiece 2 can be burnished by the tool 3 to a certain degree. After a'certain period of burnishing the tooth surfaces (a) and (c) of the workpieces 1 and 2, the hydraulic cylinder 25 is reverted to its original position. The original position of the hydraulic cylinder is detected by dog 149 and limit switch 148, shown in FIG. 17.

Next, the hydraulic cylinder 25 is actuated in the opposite direction to move the rack 24 in the direction of decelerating the workpiece 1, thereby shifting the rack 24 in the opposite direction by a distance set by the positioning member 26. Then the tooth surfaces of the workpiece 1 and the tool 3 come into contact with each other as shown in FIG. 5; namely, the tooth surface (0) of the workpiece 1 touches the coasting side (d) of the tool 3, while the tooth surface (a) of the workpiece 2 touches only the driving side (b) of the tool 3 (as shown in FIG. 7). When in this case the rack 24 is shifted to the opposite direction a distance set by the positioning member 26, the tooth surface (c) of the workpiece l and the tooth surface (a) of the workpiece 2 will be burnished to a specified degree, and in a specified time the tooth surfaces (c) and (a) of the workpieces 1 and 2 will be burnished to a desired dimensional precision. After the tooth surfaces of the workpieces 1 and 2 have been burnished in this way, the hydraulic cylinder 25 restores the rack 24 to its original position which is detected by dog 149 and limit switch 148, and the motor 10 halts, thus concluding the finishing operation of the workpieces 1 and 2.

To revert the teeth of the workpieces 1 and 2 meshing with the tool 3 to the pre-Working position, a motor 28 is started to set the workpieces 1 and 2 running in opposite directions through a worm gear 29, a worm wheel 31), and one-way clutch 31 which can freely rotate while the motor 10 is running. Upon detecting the pre-working position of the workpieces l and 2 in relation to the tool 3 by means of a cam plate 32 and a noncontact limit switch 33, the motor 28 is stopped and the tool 3 is reset to the original position by the action of the cylinder 7, thereby concluding the finishing operation of the workpieces 1 and 2.

Apparatus corresponding to the system schematically diagramed in FIG. 2, is more fully illustrated in FIGS. 15-22. Elements of the apparatus illustrated in FIGS. 15-22 are identified by the same reference numerals used in FIG. 2, and FIGS. 15-22 point out further features of the apparatus. FIG. 15 is a plan view of the apparatus more clearly showing the relationship of its parts, and especially the relationship of the hypoid pinion gears l and 2 to the hypoid ring gear 3. FIG. 16 is a side view of the apparatus illustrated in FIG. 15. FIGS. 15 and 16 show apparatus base and housing 139 to which upstanding column 140 is attached, from which slide bases 141 and 141 extend, upon which gear heads 143 and 143' are slidably mounted by slides 142 and 142. Below the slide bases, planetary gear casings 144 and 144' extend in positions substantially below gear heads 143 and 143, respectively. Working head 145 of the hypoid ring gear 3 is supported on wing base 147 attached to plate 146, and located with the axis of working head 145 normal to the major axes of gear heads 143 and 143. Working head 145 which is slidably mounted on wing base 147 also has dog 1511 mounted thereon for tripping limit switch 151 to limit the sliding movement of working head 145 toward the gear heads 143 and 143'.

FIGS. 17-20, and FIG. 22 show cross-sectional views of various portions of the apparatus illustrated in FIGS. 15 and 16. FIG. 17 is a cross-sectional view along line A-A of FIG. 15 through gear head 143 and planetary gear casing 144, more clearly showing the relationship between the planetary gears and the bevel gears within the gear heads. FIG. 17 also illustrates in more detail the relationship of internal gear 17 in the planetary gear system with rack 24 which reciprocates between stops 26 and 27, and is driven by cylinder 25. As already noted herein, hydraulic cylinder 25 may be reverted to its original position which is detected by dog 149 in combination with limit switch 148. As rach 24 moves toward positioning member 26 the tooth surfaces of the workpieces l and 2 are changed with respect to the hypoid ring gear or tool 3, providing twisting torque so that the surfaces of the workpieces may be burnished. As rack 24 is moved by piston 25 to the position set by positioning member 27, the workpieces l and 2 are twisted by tool 3 so that the opposite tooth surfaces of the workpieces are burnished. When the piston 25 is returned to its original position, it is locked in that position by a valve (not shown) to prevent the internal gear 17 from rotating when drive motor is engaged.

FIG. 18 is a cross-sectional view of the apparatus illustrated in FIG. taken along line BB, showing the structure of the base or housing 139 in which shafts 57 and 58 are rotatably mounted having bevel gears 14, 14, and 16, 16' mounted on the respective ends of shafts 58 and 57. FIG. 18 also shows drive motor 10 which propels bevel gear 13 with which bevel gears 14 and 14 are engaged. Shaft 57 carries worm wheel 30 which may be engaged and disengaged with shaft 57 by one-way clutch 31. Worm wheel 30 meshes with worm 29 which is connected to motor 28 which is also attached to base 139. Shaft 58 carries cam plate 32 and limit switch 33 mounted on base 139. Dog 156 mounted on cam plate 32 may be adjusted around the periphery of the cam plate. In operation, as the oneway clutch 31 is rotated by the motor 28 in the direction to rotate the shaft 57, said shaft is rotated by Worm 29 and worm wheel 30, while shaft 58 is rotated until the shafts reach the position set in the cam plate-limit switch system. By that time, the faces of the teeth of the workpieces 1 and 2, and tool 3 will have returned to their original positions. Cam plate 32 and limit switch 33 work only for returning faces of the workpieces 1 and 2 in order that the tool 3 properly engages the next workpieces 1 and 2 when the tool 3 is adjusted by hydraulic cylinder 7, as shown in FIG. 2.

FIG. 19 is a cross-sectional view of the apparatus of FIG. 15 taken along line C-C showing the relationship of the bevel gear system 15, I6 and planetary gear system 17, 18, 19, which drives bevel gear 21. FIG. is a cross-sectional view of the apparatus illustrated in FIG. 15 taken along line DD, showing the internal structure of working head 145 which is mounted on wing base 147 and slidably moved by a piston in cylinder 7. The shaft 8 attached to said piston is stopped at a specified position by the positioning member 9 adjustably mounted in plate 146. FIG. 20 also illustrates the relationship between brake lever 11 and brake drum 12 on shaft 6, all of which are further illustrated in FIG. 21. The rotation of shaft 6, which carries the ring gear 3, is braked when lever 11 with brake drum 12.

FIG. 22 is a cross-sectional view of the apparatus illustrated in FIG. 16 taken along line EE, showing the internalstructure of planetary gear system 17, 18, 19, in casing 144'. The planetary gearing system is rigidly held in the casing 144' either by the internal gear 17', or by bolt 152. The planetary gear system illustrated in FIG. 17 is similar to the structure illustrated in FIG. 22, additionally comprising an external gear on gear 17, which meshes with rach 24.

Of course, it is possible to use the system and apparatus described in conjunction with FIGS. 2 and 15-22 for the purpose of finishing the tooth surfaces of a hypoid ring gear, and this will be explained referring to the second embodiment of the present invention.

The second embodiment represents an addition of a tooth-positioning device for positioning the hypoid pinion gear with respect to the power transmission system in the first embodiment.

Just like the first one, the second embodiment needs an adjustment of the positions of hypoid pinion gears 101 and 102 (hereafter to be called the tools) and a hypoid ring gear 103 (hereafter to be called the workpiece) when they are to be meshed with one another, and this adjustment will be described in conjunction with FIG. 8. The apparatus embodying the system schematically illustrated in FIG. 8 is substantially the same as that illustrated in FIGS. 1522, additionally including the modifications shown in FIGS. 23 and 24. The reference numerals in FIGS. 8, 23 and 24 start from 101, instead of 1, as in FIGS. 2 and 15-22.

FIG. 23 is a cross-sectional view of gear head 143 similar to the respective portion of FIG. 17, but FIG. 23 additionally shows lever 134 by which shaft 104 may be turned. Lever 134 is used in conjunction with member 135 shown in FIG. 8, to match the faces of the teeth of tools 101 and 102. Member 134 is detachably engaged with shaft 104 so that it may be engaged with shaft 104 to lock the shaft against rotation, and disengage therewith to allow shaft 104 to freely rotate.

FIG. 24 illustrates a cross-sectional view through planetary gear casing 144', similar to FIG. 22, additionally showing a worm wheel in combination with internal gear 17', with the worm wheel engaged with worm gear 137 which may be turned by rotating handle 136, and locked in place by set screw 153. After matching the faces of the teeth of tools 101 and 102 with the teeth of ring gear 103, worm gear 137 is locked so that internal gear 117' is unable to rotate, and the planetary gear system is operable in its normal fashion.

Using such a tooth-positioning device, a hypoid ring gear (hereafter to be called master gear) finished to normal size and tooth contact by the conventional process, is fitted to the tip of a shaft 106 in a position matching the teeth of the tools 101 and 102 attached to the inside ends of shafts 104 and 105. A hydraulic cylinder I07 linked to the shaft 106 is operated to move the master gear into a position just short of engaging the tools 101 and 102. This position is detected by dog 150 and limit switch 151, as shown in FIG. 16. Then, with the shaft 104 locked by operation of lever member 134 attached to shaft 104, the shaft is set in a rotatable state by operation of a similar lever member 135 attached to shaft 105. Rotation of a handle 136 in one direction, with shafts 104 and 105 set in this state, will be transmitted via worm gear 137 which is consolidated with handle 136, to the internal teeth of the planetary reducing system integrated with the worm-wheel. This planetary reducing system comprises internal gear 117', sun gear 118', and planet gear 119'. With sun gear 118' locked in this case, rotation of the internal gear 117 causes rotation of planet gear 119'. The revolution of planet gear 119 around sun gear 118 causes rotation of a bevel gear 120'. Thus, the rotation of handle 136, which has been transmitted to internal gear 117 is transmitted via bevel gear 120' to a bevel gear 121, and further via a bevel gear 122' engaged with the bevel gear 121', and via a bevel gear 123 fixed to shaft 105, which has been set in a rotatable state by operation of lever member 135.

Thus, when the handle 136.is turned in one direction until the tool 102, which is fitted to the inner end of shaft 105, comes into proper mesh with the master gear, the lever member is operated to lock the rotation of the shaft 105.

Next, the shaft 104, which has been locked, is liberated to freely turn by operation of lever member 134, and handle 136 is turned in the direction rendering one-way clutch 131 freely rotatable in relation to worm-wheel 130. Hence, sun gear 118' is in a freely rotatable state, while the bevel gear 120' is in a locked condition. Therefore, movement of handle 136 is transmitted via worm gear 137 and internal gear 117' of the planetary reducing system with the sun gear 118, and via a bevel gear 116, moving together with the sun gear 118, to a bevel gear 115. Further, the movement is transmitted to the bevel gears 113 and 114 via a bevel gear 114 moving together with bevel gear 115', bevel gears 113 and 114, a bevel gear 115 moving together with a bevel gear 114, a bevel gear 116, the planetary reducing system composed of the internal gear 117, a sun gear 118 and a planet gear 119, and then to bevel gears 122 and 123 moving together with a bevel gear 121. Rotation of shaft 104, beings tool 101 at the end of the shaft 104 into proper engagement with the master gear.

Thus, when the tools 101 and 102 are brought to the position of properly engaging the master gear, the lever 135 is operated to set the-shaft 105 free to rotate, the worm 137 is held immovable by set screw 153, and the hydraulic cylinder 107 is operated to move the master gear, which is now close to the tools 101 and 102, forward to engage the tools 101 and 102. Through adjustment of the positioning members 108 and 109 for the shaft 106, an adequate gap is provided circumferentially between the teeth of the tools 101 and 102, and the master gear 103. Red lead is then applied to the master gear. Thereafter, a motor 110 is stated, and, with brake drum 112 on the shaft 106, being braked by the operation of a brake lever 111, the tooth contact of the master gear against the tools 101 and 102 is checked. The shafts 104 and 105 of the tools 101 and 102 are adjusted in the longitudinal directions of the shafts 104 and 105 normal to the direction of shaft 106 of the master gear, so that an appropriate tooth contact may be established on the tooth surface of the master gear.

After the position of the tools 101 and 102 relative to the master gear has been adjusted in this way, the workpiece is finished in the following manner:

The master gear is taken away from the shaft 106 and instead, the workpiece 103 is fitted on the shaft 106.

The hydraulic cylinder 107 is operated to move the workpiece 103 to engage the tools 101 and 102. Then the motor 110 is started, rotating in the direction illustrated, for instance, in FIG. 1. The rotation of the motor 110, just as in the first embodiment, causes the same amount of rotation of the tools 101 and 102 in the opposite direction, thereby turning the workpiece 103.

the workpiece 3 and the tools 101 and 102 in the above condition is illustrated in FIG. 3. Namely, the tooth surface (a) of the tool 101 is in contact only with the driving side (b) of the workpiece 103 (see FIG. 4), while the tooth surface (0) of the tool' 102 is in contact only with the coasting side (d) of the workpiece 103 (see FIG. 6). This tooth contact relationship is also illustrated in FIGS. 9 and 10, which are cross-sectional views of the hypoid gear system illustrated in FIG. 1, taken along lines lX-IX'and XX, respectively. In this case, hydraulic cylinder is operated to move the rack 124, and the tool 101 thereby finishes the driving side (b) of the workpiece 1, while the tool 102 finishes the coasting side (d) of it. As the rack 124 is shifted over the distance set by the positioning members 126 and 127 in the axial direction, and the shaft 106 is moved a distance set by positioning members 108 and 109, the tooth surface of the workpiece 103 is burnished to the desired tooth thickness. As the finish ing continues, a contact line (-2) as indicated in FIG. 11 is formed between the driving side (b) of the workpiece 103 and the tool 101. and this contact line (2) moves in the direction (I), depending on the engagement of the workpiece 103 and the tool 101, until the tool 101 comes to cover the whole driving side (b) of the workpiece 103. Meanwhile the coasting side (d) of the workpiece 103 and the tool 102 are in contact with each other on a line (g) indicated in FIG. 12. Depending on the engagement of the workpiece 103 and the tool 102, the line (g) moves in the direction (h) until it covers the whole coasting side (d) of the workpiece 103.

As seen in the vertical section of the tooth trace in FIG. 13, the driving side (b) of the workpiece 103 is burnished in the direction (1'), while the coasting side ((1) is burnished in the direction (j). Thus, with the trace running in the direction (i) on the driving side (b), the workpiece 103 has a swelling (k) at the tooth tip, but on the coasting side (d) where the trace runs in the direction (i), there is no swelling at the tooth tip. The swelling (k) formed at the tooth tip on the driving side (b) of the workpiece 103 is small, but if necessary, it can be removed. After the burnishing of the tooth surfaces of the workpiece 103, the hydraulic cylinder 125 restores the rack 124 to the initial position, the motor 110 stops, and the finishing of the workpiece 103 is concluded. For the purpose of reverting the teeth of tools 101 and 102 to the pre-working position, a motor 128 is started to make the tools 101 and 102 run in reverse direction through a worm gear 129, a worm wheel 130 and the one-way clutch 131, which can freely rotate while the motor 110 is running. Through cam plate 132, dog 156, and a non-contact limit switch 133, the tools 101 and 102 are reverted to the pre-working position, thereby completing the finishing process of the workpiece 103.

It goes witnout saying that even in the second embodiment the tooth surfaces of hypoid pinion gears can be finished. For the particular purpose of finishing only the surfaces of the hypoid ring gear, the power transmission system of a structure as schematically illustrated in FIG. 14 can be utilized. Elements 101 112 in FIG. 14 are like the corresponding elements in FIGS. 2, 8, l5, 16, 20 and 21. Instead of using the planetary reducing system as illustrated in FIG. 8, a twisting torque can be given to the tools 101 and 102 by means of the brake 138, and the same effect as in the embodiment shown in FIG. 8 can thereby attained.

FIG. 25 is a cross-sectional view of apparatus embodying the system schematically illustrated in FIG. 14, taken along the axes or shafts 104 and 105. Motor 110 Cal drives sun gear 118' of planetary gear system 117, 118', 119, which is similar to the system illustrated in FIG. 24. Shaft 105-is connected to planet gears 118'. The embodiment of FIGS. 14 and 25 differs from that illustrated in FIGS. 2 and 8 in that the tool 101 is always given braking torque during processing by the brake 138, brake shoe 154 and cylinder 155 so that the workpiece 103 is continuously burnished.

To match the faces of the teeth of the tool 101 and 102, the apparatus illustrated in FIG. 25 is used by first locking the rotation of the motor by means not shown, and then rotating handle 136 thereby rotating internal gear 117 so that the rotation is transmitted to too] 102 because the sun gear 119' is locked with the motor. Worm 137 is locked with set screw 153 during this face matching operation. After matching the faces of the tools 101 and 102, the worm gear 137 locked in casing 144' so that the internal gear 117 is unable to rotate.

As described above, the present invention is an apparatus and method for burnishing with a combination of a tool-gear finished to a specified shape and a workpiece-gear which has been rough-cut. Merits of the present invention are that the tooth surface of a gear can be finished smooth to a desired precision and the best tooth contact can be assured. As compared with the conventional process, the work efficiency rises several times while saving work expense, and the tool life is substantially prolonged What is claimed is:

l. A method for finishing the tooth surfaces of a hypoid gear which comprises a hypoid ring gear and a pair of hypoid pinion gears, wherein said pair is a finished tool and said ring gear is a rough-cut gear, comprising:

meshing said pair of hypoid pinion gears with the hypoid ring gear; and

applying torques to said pinion gears in opposite directions rotating one of pinion gears having its toothed surfaces in contact with the driven side of the tooth surfaces of said rough-cut hypoid ring gear, and braking the rotation of the other of said hypoid pinion gears whose tooth surfaces are in contact with the braked side of the tooth surfaces of said rough-cut hypoid ring gear, thereby turning said ring gear and simultaneously burnishing both sides of the tooth surfaces of the rough-cut hypoid gear by running contact with the tooth surfaces of the tool gears.

2. an apparatus for finishing the tooth surfaces of a hypoid gear which comprises a hypoid ring gear and a pair of hypoid pinion gears, wherein one of said ring gears and said pair is a finished tool and the other of said ring gear and said pair is a rough-cut gear, comprising:

means for rotatably mounting a hypoid ring gear;

means for axially advancing said hypoid ring gear into meshing engagement with a pair of rotatably mounted hypoid pinion gears whose axes lie in a plane which is substantially perpendicular to the axis of said hypoid ring gear; and

means for rotating said pinion gears, said rotating means including a planetary reducing system for regulating the running speed of said hypoid pinion gears, so that the tooth surfaces of one of said pinion gears contact the one side surface of each tooth of said hypoid ring gear, and the tooth surfaces of the other pinion gear of said pair contact the other side surface of each tooth of said hypoid ring gear.

3. The apparatus of claim 2, wherein said planetary reducing system includes means for locking the internal gear of said planetary gear system against rotation.

4. The apparatus of claim 2, additionally comprising mans for changing the direction of rotation of said pinion gears with respect to said ring gear by reversing the surfaces of the teeth of said hypoid ring gear which are contacted by the tooth surfaces of the hypoid pinion gears.

5. The apparatus of claim 4, wherein said means for changing the direction of rotation of said pinion gears with respect to said ring gear comprises means for rotating an internal gear of said planetary reducing system.

6. The apparatus of claim 5, wherein said means for rotating the internal gearof said planetary reducing system comprises an external pinion gear on the internal gear, engaging a rack for rotating said internal gear.

7. The apparatus of claim 5, wherein the means for rotating the internal gear of said planetary reducing system comprises an external worm-wheel gear on said internal gear, engaging a rotatable worm gear for rotating said internal gear.

8.The apparatus of claim 6, additionally comprising stopping means located at both ends of said rack for limiting the length of movement of said rack, and a reciprocating hydraulic piston for moving said rack back and forth between said stops.

9. The apparatus of claim 2, additionally comprising shafts upon which each of said hypoid pinion gears is rotatable, and means for locking rotation of each of said shafts during alignment of the tooth faces of said hypoid pinion gears with the tooth faces of said hypoid ring gear.

10. The apparatus of claim 2, wherein said means for advancing said hypoid ring gear into axial meshing engagement with the pair of rotatably mounted hypoid pinion gears comprises a hydraulic piston.

' 11. The apparatus of claim 10, wherein said means for advancing said hypoid ring gear additionally comprises a stopping means rigidly fixed onthe means for rotatably mounting said hypoid ring gear, and a second stopping means located in the path of movement of said first stopping means for stopping the axial advancement of said hypoid ring gear.

12. The apparatus of claim 2, wherein said means for rotating said pinion gears includes a plurality of shafts connected by a plurality of bevel gears.

13. The apparatus of claim 2, additionally comprising means for axially advancing each of said rotatably mounted hypoid pinion gears toward its position of engagement with the hypoid ring gear.

14. An apparatus for finishing the tooth surfaces of a hypoid gear which comprises a hypoid ring gear and a pair of hypoid pinion gears, wherein one of said ring gear and said pair is a finished tool and the other of said ring gear and said pair is a rough-cut gear, comprising:

means for rotatably mounting a hypoid ring gear;

means for axially advancing said hypoid ring gear into meshing engagement with a pair of rotatably mounted hypoid pinion gears whose axes lie in a lit plane which issubstantially perpendicular to the axis of said hypoid ring gear; and

means for rotating said pinion gears so that the tooth surfaces of one of said pinion gears contact the one side surface of each tooth of said hypoid ring gear, and the tooth surfaces of the other pinion gear of said pair contact the other side surface of each tooth of said hypoid ring gear; wherein said means for rotating said pinion gears includes at least one rotatable shaft, and said shaft carries a rotatable plate having a camming surface on the periphery of said plate, which camming surface is engageable with a limit switch adjacent said surface;

a clutch for reversing the direction of rotation of said hypoid pinion gears for returning said hypoid pinion gears to a pre-working position; and

said clutch is connected for operation in response to the tripping of said limit switch by said cam plate.

15. A method of finishing the tooth surfaces of a hypoid gear which comprises a hypoid ring gear and a pair of hypoid pinion gears, wherein one of said ring gears and said pair is a finished tool and the other of said ring gear and said pair is a rough-cut gear, comprising:

meshing said pair of hypoid pinion gears with the hypoid ring gear; rotating the hypoid ring gear by increasing and decreasing the rotating speed of either one of said pair of hypoid pinion gears; and

pressure-contacting the mutually meshed tooth surfaces of said tool with said rough-cut gear in the pitch circle direction of said gear, thereby deforming both tooth surfaces of said rough-cut gear.

16. The method of claim 15, wherein the hypoid ring gear is the rough-cut gear, and the pair of hypoid pinion gears is the tool, comprising increasing or decreasing a rotating speed of one of said pinion gears, pressurecontacting the tooth surface of one of said tools with the surfaces of one side of said hypoid ring gear teeth and at the same time, pressure-contacting the tooth surface of the other of said tool with the surfaces of the other side of said hypoid ring gear teeth, thereby simultaneously burnishing both sides of the tooth surfaces of said rough-cut hypoid ring gear.

17. An apparatus for finishing the tooth surfaces of a hypoid gear which comprises a hypoid ring gear and a pair of hypoid pinion gears, wherein one of said ring gear and said pair is a finished tool and the other of said ring gear and said pair is a rough-cut gear, comprising:

means for rotatably mounting a hypoid ring gear; means for axially advancing said hypoid ring gear into meshing engagement with a pair of rotatably mounted hypoid pinion gears whose axes lie in a plane which is substantially perpendicular to the axis of said hypoid ring gear;

means for rotating each gear of said pair of hypoid pinion gears; and

means for regulating the rotating speed of one of said hypoid pinion gears, which means is arranged in the means for rotating each gear of said pair of hypoid pinion gears.

18. The apparatus of claim 17, wherein the means for rotating each gear of said pair of hypoid pinion gears comprises only one source of rotary motion.

19. The apparatus of claim 17', wherein the means for regulating the rotating speed is a planetary gear system comprising a sun gear; a sun and planet gear, an internal gear and a carrier supporting said sun and planet gear.

20. The apparatus of claim 19, wherein said planetary gear system includes means for locking the internal gear of said planetary gear system against rotation.

21. The apparatus of claim 19, wherein said planetary gear system includes means for rotating the internal gear to regulate the rotating speed of one of said pair of hypoid pinion gears.

22. The apparatus of claim 21, wherein said means for rotating the internal gear of said planetary gear system comprises an external pinion gear on the internal gear, engaging a rack for rotating said internal gear.

23. The apparatus of claim 21, wherein the means for rotating the internal gear of said planetary gear system comprises an external worm-wheel gear on said internal gear, engaging a rotatable wonn gear for rotating said internal gear.

24. The apparatus of claim 17, wherein said means for rotating said pinion gears includes at least one rotatable shaft, and said shaft carries a rotatable plate having a camming surface on the periphery of said plate, which camming surface is engageable with a limit switch adjacent said surface;

a clutch for reversing the direction of rotation of said hypoid pinion gears for returning said hypoid pinion gears to a pre-working position; and

said clutch is connected for operation in response to the tripping of said limit switch by said cam plate.

25. The apparatus of claim 22, additionally comprising stopping means located at both ends of said rack for limiting the length of movement of said rack, and a reciprocating hydraulic piston for moving said rack back and forth between said stops.

v UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3, 813,821 D t d June 4, 1974 Patent No.

Inve t AKIRA TAKAHASHI et :11

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claims 4 and 5 should read as follows:

4', r The apparatus of Claim 2,, additionally comprising means for reversing the surfaces of teeth of said hypoid ring gear which are contacted by the tooth surfaces of the hypoid pinion gears.

' 5 '9 The apparatus of Claim 4 wherein said reversing planetary reducing system.

Signed and sealed this 24th day of September 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. Attesting Officer C. MARSHALL DANN Commissioner of Patents 2 FORM PO-1050 (10-69) USCOMMQDC 603754091" a 5; GOVERNMENT 'RlNTlNG OFHCE: I'l O-JE'ZSQ'. 

1. A method for finishing the tooth surfaces of a hypoid gear which comprises a hypoid ring gear and a pair of hypoid pinion gears, wherein said pair is a finished tool and said ring gear is a rough-cut gear, comprising: meshing said pair of hypoid pinion gears with the hypoid ring gear; and applying torques to said pinion gears in opposite directions rotating one of pinion gears having its toothed surfaces in contact with the driven side of the tooth surfaces of said rough-cut hypoid ring gear, and braking the rotation of the other of said hypoid pinion gears whose tooth surfaces are in contact with the braked side of the tooth surfaces of said rough-cut hypoid ring gear, thereby turning said ring gear and simultaneously burnishing both sides of the tooth surfaces of the rough-cut hypoid gear by running contact with the tooth surfaces of the tool gears.
 2. an apparatus for finishing the tooth surfaces of a hypoid gear which comprises a hypoid ring gear and a pair of hypoid pinion gears, wherein one of said ring gears and said pair is a finished tool and the other of said ring gear and said pair is a rough-cut gear, comprising: means for rotatably mounting a hypoid ring gear; means for axially advancing said hypoid ring gear into meshing engagement with a pair of rotatably mounted hypoid pinion gears whose axes lie in a plane which is substantially perpendicular to the axis of said hypoid ring gear; and means for rotating said pinion gears, said rotating means including a planetary reducing system for regulating the running speed of said hypoid pinion gears, so that the tooth surfaces of one of said pinion gears contact the one side surface of each tooth of said hypoid ring gear, and the tooth surfaces of the other pinion gear of said pair contact the other side surface of each tooth of said hypoid ring gear.
 3. The apparatus of claim 2, wherein said planetary reducing system includes means for locking the internal gear of said planetary gear system against rotation.
 4. The apparatus of claim 2, additionally comprising mans for changing the direction of rotation of said pinion gears with respect to said ring gear by reversing the surfaces of the teeth of said hypoid ring gear which are contacted by the tooth surfaces of the hypoid pinion gears.
 5. The apparatus of claim 4, wherein said means for changing the direction of rotation of said pinion gears with respect to said ring gear comprises means for rotating an internal gear of said planetary reducing system.
 6. The apparatus of claim 5, wherein said means for rotating the internal gear of said planetary reducing system comprises an external pinion gear on the internal gear, engaging a rack for rotating said internal gear.
 7. The apparatus of claim 5, wherein the means for rotating the internal gear of said planetary reducing system comprises an external worm-wheel gear on said internal gear, engaging a rotatable worm gear for rotating said internal gear.
 8. The apparatus of claim 6, additionally comprising stopping means located at both ends of said rack for limiting the length of movement of said rack, and a reciprocating hydraulic piston for moving said rack back and forth between said stops.
 9. The apparatus of claim 2, additionally comprising shafts upon which each of said hypoid pinion gears is rotatable, and means for locking rotation of each of said shafts during alignment of the tooth faces of said hypoid pinion gears with the tooth faces of said hypoid ring gear.
 10. The apparatus of claim 2, wherein said means for advancing said hypoid ring gear into axial meshing engagement with the pair of rotatably mounted hypoid pinion gears comprises a hydraulic piston.
 11. The apparatus of claim 10, wherein said means for advancing said hypoid ring gear additionally comprises a stopping means rigidly fixed on the means for rotatably mounting said hypoid ring gear, and a second stopping means located in the path of movement of said first stopping means for stopping the axial advancement of said hypoid ring gear.
 12. The apparatus of claim 2, wherein said means for rotating said pinion gears includes a plurality of shafts connected by a plurality of bevel gears.
 13. The apparatus of claim 2, additionally comprising means for axially advancing each of said rotatably mounted hypoid pinion gears toward its position of engagement with the hypoid ring gear.
 14. An apparatus for finishing the tooth surfaces of a hypoid gear which comprises a hypoid ring gear and a pair of hypoid pinion gears, wherein one of said ring gear and said pair is a finished tool and the other of said ring gear and said pair is a rough-cut gear, comprising: means for rotatably mounting a hypoid ring gear; means for axially advancing said hypoid ring gear into meshing engagement with a pair of rotatably mounted hypoid pinion gears whose axes lie in a plane which is substantially perpendicular to the axis of said hypoid ring gear; and means for rotating said pinion gears so that the tooth surfaces of one of said pinion gears contact the one side surface of each tooth of said hypoid ring gear, and the tooth surfaces of the other pinion gear of said pair contact the other side surface of each tooth of said hypoid ring gear; wherein said means for rotating said pinion gears includes at least one rotatable shaft, and said shaft carries a rotatable plate having a camming surface on the periphery of said plate, which camming surface is engageable with a limit switch adjacent said surface; a clutch for reversing the direction of rotation of said hypoid pinion gears for returning said hypoid pinion gears to a pre-working position; and said clutch is connected for operation in response to the tripping of said limit switch by said cam plate.
 15. A method of finishing the tooth surfaces of a hypoid gear which comprises a hypoid ring gear and a pair of hypoid pinion gears, wherein one of said ring gears and said pair is a finished tool and the other of said ring gear and said pair is a rough-cut gear, comprising: meshing said pair of hypoid pinion gears with the hypoid ring gear; rotating the hypoid ring gear by increasing and decreasing the rotating speed of either one of said pair of hypoid pinion gears; and pressure-contacting the mutually meshed tooth surfaces of said tool with said rough-cut gear in the pitch circle direction of said gear, thereby deforming both tooth surfaces of said rough-cut gear.
 16. The method of claim 15, wherein the hypoid ring gear is the rough-cut gear, and the pair of hypoid pinion gears is the tool, comprising increasing or decreasing a rotating speed of one of said pinion gears, pressure-contacting the tooth surface of one of said tools with the surfaces of one side of said hypoid ring gear teeth and at the same time, pressure-contacting the tooth surface of the other of said tool with the surfaces of the other side of said hypoid ring gear teeth, thereby simultaneously burnishing both sides of the tooth surfaces of said rough-cut hypoid ring gear.
 17. An apparatus for finishing the tooth surfaces of a hypoid gear which comprises a hypoid ring gear and a pair of hypoid pinion gears, wherein one of said ring gear and said pair is a finished tool and the other of said ring gear and said pair is a rough-cut gear, comprising: means for rotatably mounting a hypoid ring gear; means for axially advancing said hypoid ring gear into meshing engagement with a pair of rotatably mounted hypoid pinion gears whose axes lie in a plane which is substantially perpendicular to the axis of said hypoid ring gear; means for rotating each gear of said pair of hypoid pinion gears; and means for regulating the rotating speed of one of said hypoid pinion gears, which means is arranged in the means for rotating each gear of said pair of hypoid pinion gears.
 18. The apparatus of claim 17, wherein the means for rotating each gear of said pair of hypoid pinion gears comprises only one source of rotary motion.
 19. The apparatus of claim 17, wherein the means for regulating the rotating speed is a planetary gear system comprising a sun gear; a sun and planet gear, an internal gear and a carrier supporting said sun and planet gear.
 20. The apparatus of claim 19, wherein said planetary gear system includes means for locking the internal gear of said planetary gear system against rotation.
 21. The apparatus of claim 19, wherein said planetary gear system includes means for rotating the internal gear to regulate the rotating speed of one of said pair of hypoid pinion gears.
 22. The apparatus of claim 21, wherein said means for rotating the internal gear of said planetary gear system comprises an external pinion gear on the internal gear, engaging a rack for rotating said internal gear.
 23. The apparatus of claim 21, wherein the means for rotating the internal gear of said planetary gear system comprises an external worm-wheel gear on said internal gear, engaging a rotatable worm gear for rotating said internal gear.
 24. The apparatus of claim 17, wherein said means for rotating said pinion gears includes at lEast one rotatable shaft, and said shaft carries a rotatable plate having a camming surface on the periphery of said plate, which camming surface is engageable with a limit switch adjacent said surface; a clutch for reversing the direction of rotation of said hypoid pinion gears for returning said hypoid pinion gears to a pre-working position; and said clutch is connected for operation in response to the tripping of said limit switch by said cam plate.
 25. The apparatus of claim 22, additionally comprising stopping means located at both ends of said rack for limiting the length of movement of said rack, and a reciprocating hydraulic piston for moving said rack back and forth between said stops. 